Growth hormone mediates zone-specific gene expression in liver.

The CYP2B1/2 gene pair is an example of many liver genes that exhibit a characteristic zonated expression pattern in the liver. The factors governing this zonation are poorly understood. We observed that after hypophysectomy the expression of CYP2B1/2 protein and mRNA in the normally silent periportal (upstream) region was high, in both male and female rats. Treatment with growth hormone counteracted the effect of hypophysectomy, limiting expression to the perivenous (downstream) region, completely in females and partially in males. This shows that a hormone zone-specifically regulates gene expression in the liver.